Passive Transport of Water into Cell by Aquaporin-2 Phosphorylated on Serine256 Aquaporin-2 (AQP2) passively transports water across membranes according to the osmotic gradient. AQP2 is mainly expressed in principal cells of the collecting duct and connecting tubule in the kidney. AQP2 function is acutely regulated by the antidiuretc hormone vasopressin. In the presence of vasopressin AQP is phosphorylated at Ser256, As inferred from rat and mouse Ser261, Ser264, and Thr269 may also be phosphorylated. These phosphorylations are thought to influence AQP2 trafficking and compartmentalization. Authored: May, B, 2009-08-06 Edited: May, B, 2009-08-06 Pubmed11076974 Pubmed15703994 Pubmed19144687 Pubmed7510718 Pubmed7535000 Pubmed8140421 Pubmed9829975 Reactome Database ID Release 43432065 Reactome, http://www.reactome.org ReactomeREACT_23788 Reviewed: Beitz, E, 2010-06-24 Reviewed: Calamita, G, 2010-07-15 Reviewed: Mathai, JC, MacIver, B, 2010-07-31